mysql重复写入数据库

ALTER TABLE users ADD UNIQUE (email);

INSERT IGNORE INTO users (id, name, email) VALUES (1, 'Alice', 'alice@example.com');

REPLACE INTO users (id, name, email) VALUES (1, 'Alice', 'alice@example.com');

START TRANSACTION;
SELECT * FROM users WHERE email = 'alice@example.com' FOR UPDATE;
INSERT INTO users (id, name, email) VALUES (1, 'Alice', 'alice@example.com');
COMMIT;

import mysql.connector

db = mysql.connector.connect(host="localhost", user="user", password="password", database="mydatabase")
cursor = db.cursor()

email = 'alice@example.com'
cursor.execute("SELECT * FROM users WHERE email = %s", (email,))
result = cursor.fetchone()

if not result:
    cursor.execute("INSERT INTO users (id, name, email) VALUES (%s, %s, %s)", (1, 'Alice', email))
    db.commit()
else:
    print("Email already exists")

cursor.close()
db.close()